Joe,

The default century in VFP is 19. SET CENTURY on and off only effects the display of a date in showing or not showing the first two digits of the year.

Here's the comadn you want to get the behavior you are asking about;

SET CENTURY TO 19 ROLLOVER 90 (or some other year)

This command makes all dates that end with 90 or higher to be 19 and any dates less than 90 will be 20.